Sound absorbing materials have been used heretofore in many fields and are often used typically for walls and ceilings of anechoic room.
A specific example of such sound absorbing materials generally used is a combination of plate-shaped sound absorbing components in which woven cloth covers a porous material such as glass wool. These components are suitably applicable to applications in a relatively large scale such as the anechoic room, but are not suitable for sound absorbing components for automobile such as components in an automobile engine room including an automobile engine cover. Requirements for sound absorbing components for automobile are capability of being used in a limited space and capability of exhibiting a sufficient sound absorbing effect. The conventional sound absorbing materials as described above, however, has a lot of problems; for example, it was not easy to freely shape them so as to be compatible with the space, their sound absorbing performance was degraded by absorption of oil or water, an increase of the weight due to the absorption of oil or water made retention of the shape difficult, and so on.
Also known are sound absorbing materials using a foamed body having isolated cells, i.e., cells not communicating with each other. They had, however, problems that the mechanical strength was poor and that a sufficient sound absorbing effect was not attained especially in the high-frequency region.
Further, the sound absorbing components for automobile, such as those for automobile engine and its surroundings, must have not only excellent sound absorbing performance, but also be light in weight. In addition, since they are used in a narrow limited space, the sound absorbing components themselves are required to be compact and thin. Therefore, the sound absorbing components for automobile are excellent in the sound absorbing performance even if being thin and to be readily producible even if being compact. However, the sound absorbing components conventionally known are inadequate in these respects.
An object of the present invention is to provide a sound absorbing component which can be readily produced not only in a relatively large scale, but also in the form of a compact sound absorbing component, which is excellent in the sound absorbing performance even if lightweight and compact, and which can effectively absorb the sound, especially, in the frequency region 500 to 3000 Hz of exterior noise considered to be problematic in automobiles.